Pestiviruses and flaviviruses belong to the Flaviviridae family of viruses along with hepatitis C virus. The pestivirus genus includes bovine viral diarrhea virus (BVDV), classical swine fever virus (CSFV, also called hog cholera virus) and border disease virus (BDV) of sheep (Moennig, V. et al. Adv. Vir. Res. 1992, 41, 53-98). Pestivirus infections of domesticated livestock (cattle, pigs and sheep) cause significant economic losses worldwide. BVDV causes mucosal disease in cattle and is of significant economic importance to the livestock industry (Meyers, G. and Thiel, H.-J., Advances in Virus Research, 1996, 47, 53-118; Moennig V., et al, Adv. Vir. Res. 1992, 41, 53-98).
Human pestiviruses have not been as extensively characterized as the animal pestiviruses. However, serological surveys indicate considerable pestivirus exposure in humans. Pestivirus infections in man have been implicated in several diseases including congenital brain injury, infantile gastroenteritis and chronic diarrhea in human immunodeficiency virus (HIV) positive patients. M. Giangaspero et al., Arch. Virol. Suppl., 1993, 7, 53-62; M. Giangaspero et al., Int. J. Std. Aids, 1993, 4 (5): 300-302.
The flavivirus genus includes more than 68 members separated into groups on the basis of serological relatedness (Calisher et al., J. Gen. Virol, 1993, 70, 37-43). Clinical symptoms vary and include fever, encephalitis and hemorrhagic fever. Fields Virology, Editors: Fields, B. N., Knipe, D. M., and Howley, P. M., Lippincott-Raven Publishers, Philadelphia, Pa., 1996, Chapter 31, 931-959. Flaviviruses of global concern that are associated with human disease include the dengue hemorrhagic fever viruses (DHF), yellow fever virus, shock syndrome and Japanese encephalitis virus. Halstead, S. B., Rev. Infect. Dis., 1984, 6, 251-264; Halstead, S. B., Science, 239:476-481, 1988; Monath, T. P., New Eng. J. Med., 1988, 319, 641-643.
Examples of antiviral agents that have been identified as active against the flavivirus or pestiviruses include:
(1) interferon and ribavirin (Battaglia, A. M. et al., Ann. Pharmacother, 2000, 34, 487-494); Berenguer, M. et al. Antivir. Ther., 1998, 3 (Suppl. 3), 125-136);
(2) Substrate-based NS3 protease inhibitors (Attwood et al., Antiviral peptide derivatives, PCT WO 98/22496, 1998; Attwood et al., Antiviral Chemistry and Chemotherapy 1999, 10, 259-273; Attwood et al., Preparation and use of amino acid derivatives as anti-viral agents, German Patent Pub. DE 19914474; Tung et al. Inhibitors of serine proteases, particularly hepatitis C virus NS3 protease, PCT WO 98/17679), including alphaketoamides and hydrazinoureas, and inhibitors that terminate in an electrophile such as a boronic acid or phosphonate (Llinas-Brunet et al, Hepatitis C inhibitor peptide analogues, PCT WO 99/07734).
(3) Non-substrate-based inhibitors such as 2,4,6-trihydroxy-3-nitro-benzamide derivatives (Sudo K. et al, Biochemical and Biophysical Research Communications, 1997, 238, 643-647; Sudo K. et al. Antiviral Chemistry and Chemotherapy, 1998, 9, 186), including RD3-4082 and RD3-4078, the former substituted on the amide with a 14 carbon chain and the latter processing a para-phenoxyphenyl group;
(4) Thiazolidine derivatives which show relevant inhibition in a reverse-phase HPLC assay with an NS3/4A fusion protein and NS5A/5B substrate (Sudo K. et al., Antiviral Research, 1996, 32, 9-18), especially compound RD-1-6250, possessing a fused cinnamoyl moiety substituted with a long alkyl chain, RD4 6205 and RD4 6193;
(5) Thiazolidines and benzanilides identified in Kakiuchi N. et al. J. FEBS Letters 421, 217-220; Takeshita N. et al. Analytical Biochemistry, 1997, 247, 242-246;
(6) A phenan-threnequinone possessing activity against protease in a SDS-PAGE and autoradiography assay isolated from the fermentation culture broth of Streptomyces sp., Sch 68631 (Chu M. et al., Tetrahedron Letters, 1996, 37, 7229-7232), and Sch 351633, isolated from the fungus Penicillium griscofuluum, which demonstrates activity in a scintillation proximity assay (Chu M. et al., Bioorganic and Medicinal Chemistry Letters 9, 1949-1952);
(7) Selective NS3 inhibitors based on the macromolecule elgin c, isolated from leech (Qasim M. A. et al., Biochemistry, 1997, 36, 1598-1607);
(8) Helicase inhibitors (Diana G. D. et al., Compounds, compositions and methods for treatment of hepatitis C, U.S. Pat. No. 5,633,358; Diana G. D. et al., Piperidine derivatives, pharmaceutical compositions thereof and their use in the treatment of hepatitis C, PCT WO 97/36554);
(9) Polymerase inhibitors such as nucleotide analogues, gliotoxin (Ferrari R. et al. Journal of Virology, 1999, 73, 1649-1654), and the natural product cerulenin (Lohmann V. et al., Virology, 1998, 249, 108-118);
(10) Antisense phosphorothioate oligodeoxynucleotides (S-ODN) complementary to sequence stretches in the 5xe2x80x2 non-coding region (NCR) of the virus (Alt M. et al., Hepatology, 1995, 22, 707-717), or nucleotides 326-348 comprising the 3xe2x80x2 end of the NCR and nucleotides 371-388 located in the core coding region of the IICV RNA (Alt M. et al., Archives of Virology, 1997, 142, 589-599; Galderisi U. et al., Journal of Cellular Physiology, 1999, 181, 251-257);
(11) Inhibitors of IRES-dependent translation (Ikeda N et al., Agent for the prevention and treatment of hepatitis C, Japanese Patent Pub. JP-08268890; Kai Y. et al. Prevention and treatment of viral diseases, Japanese Patent Pub. JP-10101591);
(12) Nuclease-resistant ribozymes (Maccjak, D. J. et al., Hepatology 1999, 30, abstract 995); and
(13) Other miscellaneous compounds including 1-amino-alkylcyclohexanes (U.S. Pat. No. 6,034,134 to Gold et al), alkyl lipids (U.S. Pat. No. 5,922,757 to Chojkier et al.), vitamin E and other antioxidants (U.S. Pat. No. 5,922,757 to Chojkier et al.), squalene, amantadine, bile acids (U.S. Pat. No. 5,846,964 to Ozeki et al.), N-(phosphonoacetyl)-L-aspartic acid, (U.S. Pat. No. 5,830,905 to Diana et al.), benzenedicarboxamides (U.S. Pat. No. 5,633,388 to Diana et al.), polyadenylic acid derivatives (U.S. Pat. No. 5,496,546 to Wang et al.), 2xe2x80x2,3xe2x80x2-dideoxyinosine (U.S. Pat. No. 5,026,687 to Yarchoan et al.), and benzimidazoles (U.S. Pat. No. 5,891,874 to Colacino et al.).
In view of the severity of diseases associated with pestiviruses and flaviviruses, and their pervasiveness in animal and man, it is an object of the present invention to provide a compound, method and composition for the treatment of a host infected with flavivirus or pestivirus.
Compounds, methods and compositions for the treatment of a host infected with a flavivirus or pestivirus infection are described that includes an effective treatment amount of a xcex2-D- or xcex2-L-nucleoside of the Formulas (I)-(XVIII), or a pharmaceutically acceptable salt or prodrug thereof.
In a first principal embodiment, a compound of Formula I, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
R1, R2 and R3 are independently H, phosphate (including mono-, di- or triphosphate and a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate;
Y is hydrogen, bromo, chloro, fluoro, iodo, OR4, NR4R5 or SR4,
X1 and X2 are independently selected from the group consisting of H, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR4, NR4NR5 or SR5; and
R4 and R5 are independently hydrogen, acyl (including lower acyl), or alkyl (including but not limited to methyl, ethyl, propyl and cyclopropyl).
In a second principal embodiment, a compound of Formula II, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate; and
Y is hydrogen, bromo, chloro, fluoro, iodo, OR4, NR4R5 or SR4;
X1 and X2 are independently selected from the group consisting of H, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR4, NR4NR5 or SR5; and
R4 and R5 are independently hydrogen, acyl (including lower acyl), or alkyl (including but not limited to methyl, ethyl, propyl and cyclopropyl).
In a third principal embodiment, a compound of Formula III, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate; and
Y is hydrogen, bromo, chloro, fluoro, iodo, OR4, NR4R5 or SR4;
X1 and X2 are independently selected from the group consisting of H, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR4, NR4NR5 or SR5; and
R4 and R5 are independently hydrogen, acyl (including lower acyl), or alkyl (including but not limited to methyl, ethyl, propyl and cyclopropyl).
In a fourth principal embodiment, a compound of Formula IV, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
R1, R2 and R3 are independently H, phosphate (including mono-, di- or triphosphate and a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate;
Y is hydrogen, bromo, chloro, fluoro, iodo, OR4, NR4R5 or SR4;
X1 is selected from the group consisting of H, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR4, NR4NR5 or SR5; and
R4 and R5 are independently hydrogen, acyl (including lower acyl), or alkyl (including but not limited to methyl, ethyl, propyl and cyclopropyl).
In a fifth principal embodiment, a compound of Formula V, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate; and
Y is hydrogen, bromo, chloro, fluoro, iodo, OR4, NR4R5 or SR4;
X1 is selected from the group consisting of H, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR4, NR4NR5 or SR5; and
R4 and R5 are independently hydrogen, acyl (including lower acyl), or alkyl (including but not limited to methyl, ethyl, propyl and cyclopropyl).
In a sixth principal embodiment, a compound of Formula VI, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate; and
Y is hydrogen, bromo, chloro, fluoro, iodo, OR4, NR4R5 or SR4;
X1 is selected from the group consisting of H, straight chained, branched or cyclic alkyl, CO-alkyl, CO-aryl, CO-alkoxyalkyl, chloro, bromo, fluoro, iodo, OR4, NR4NR5 or SR5; and
R4 and R5 are independently hydrogen, acyl (including lower acyl), or alkyl (including but not limited to methyl, ethyl, propyl and cyclopropyl).
In a seventh principal embodiment, a compound selected from Formulas VII, VIII and IX, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
Base is a purine or pyrimidine base as defined herein;
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate;
R6 is hydrogen, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, 2-Br-ethyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), CF3, chloro, bromo, fluoro, iodo, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2; and
X is O, S, SO2 or CH2.
In a eighth principal embodiment, a compound of Formulas X, XI and XII, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
Base is a purine or pyrimidine base as defined herein;
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate;
R6 is hydrogen, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chloro, bromo, fluoro, iodo, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2;
R7 is hydrogen, OR3, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chlorine, bromine, iodine, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2; and
X is O, S, SO2 or CH2.
In a ninth principal embodiment a compound selected from Formulas XIII, XIV and XV, or a pharmaceutically acceptable salt or prodrug thereof, is provided: 
wherein:
Base is a purine or pyrimidine base as defined herein;
R1, R2 and R3 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1, R2 or R3 is independently H or phosphate;
R6 is hydrogen, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chloro, bromo, fluoro, iodo, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2; and
X is O, S, SO2, or CH2.
In a tenth principal embodiment the invention provides a compound of Formula XVI, or a pharmaceutically acceptable salt or prodrug thereof: 
wherein:
Base is a purine or pyrimidine base as defined herein;
R1 and R2 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1 or R2 is independently H or phosphate;
R6 is hydrogen, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chloro, bromo, fluoro, iodo, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2;
R7 and R9 are independently hydrogen, OR2, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chlorine, bromine, iodine, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2;
R8 and R10 are independently H, alkyl (including lower alkyl), chlorine, bromine or iodine; alternatively, R7 and R9, R7 and R10, R8 and R9, or R8 and R10 can come together to form a pi bond; and
X is O, S, SO2 or CH2.
In a eleventh principal embodiment the invention provides a compound of Formula XVII, or a pharmaceutically acceptable salt or prodrug thereof: 
wherein:
Base is a purine or pyrimidine base as defined herein;
R1 and R2 are independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1 or R2 is independently H or phosphate;
R6 is hydrogen, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chloro, bromo, fluoro, iodo, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2;
R7 and R9 are independently hydrogen, OR2, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chlorine, bromine, iodine, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2;
R10 is H, alkyl (including lower alkyl), chlorine, bromine or iodine; alternatively, R7 and R9, or R7 and R10 can come together to form a pi bond; and
X is O, S, SO2 or CH2.
In an twelfth principal embodiment, the invention provides a compound of Formula XVIII, or a pharmaceutically acceptable salt or prodrug thereof: 
wherein:
Base is a purine or pyrimidine base as defined herein;
R1 and R2 independently H; phosphate (including monophosphate, diphosphate, triphosphate, or a stabilized phosphate prodrug); acyl (including lower acyl); alkyl (including lower alkyl); sulfonate ester including alkyl or arylalkyl sulfonyl including methanesulfonyl and benzyl, wherein the phenyl group is optionally substituted with one or more substituents as described in the definition of aryl given herein; a lipid, including a phospholipid; an amino acid; a carbohydrate; a peptide; a cholesterol; or other pharmaceutically acceptable leaving group which when administered in vivo is capable of providing a compound wherein R1 or R2 is independently H or phosphate;
R6 is hydrogen, hydroxy, alkyl (including lower alkyl), azido, cyano, alkenyl, alkynyl, Br-vinyl, xe2x80x94C(O)O(alkyl), xe2x80x94C(O)O(lower alkyl), xe2x80x94O(acyl), xe2x80x94O(lower acyl), xe2x80x94O(alkyl), xe2x80x94O(lower alkyl), xe2x80x94O(alkenyl), chloro, bromo, fluoro, iodo, NO2, NH2, xe2x80x94NH(lower alkyl), xe2x80x94NH(acyl), xe2x80x94N(lower alkyl)2, xe2x80x94N(acyl)2;
R7 and R9 are independently hydrogen, OR2, alkyl (including lower alkyl), alkenyl, alkynyl, Br-vinyl, O-alkenyl, chlorine, bromine, iodine, NO2, amino, loweralkylamino or di(lower-alkyl)amino;
R8 is H, alkyl (including lower alkyl), chlorine, bromine or iodine;
alternatively, R7 and R9, or R8 and R9 can come together to form a pi bond;
X is O, S, SO2 or CH2.
The xcex2-D- and xcex2-L-nucleosides of this invention may inhibit flavivirus or pestivirus polymerase activity. These nucleosides can be assessed for their ability to inhibit flavivirus or pestivirus polymerase activity in vitro according to standard screening methods. In one embodiment the efficacy of the anti-flavivirus or pestivirus compound is measured according to the concentration of compound necessary to reduce the plaque number of the virus in vitro, according to methods set forth more particularly herein, by 50% (i.e. the compound""s EC50). In preferred embodiments the compound exhibits an EC50 of less than 15 or preferably, less than 10 micromolar in vitro.
In another embodiment, the active compound can be administered in combination or alternation with another anti-flavivirus or pestivirus agent. In combination therapy, effective dosages of two or more agents are administered together, whereas during alternation therapy an effective dosage of each agent is administered serially. The dosages will depend on absorption, inactivation and excretion rates of the drug as well as other factors known to those of skill in the art. It is to be noted that dosage values will also vary with the severity of the condition to be alleviated. It is to be further understood that for any particular subject, specific dosage regimens and schedules should be adjusted over time according to the individual need and the professional judgment of the person administering or supervising the administration of the compositions.
HCV is a member of the Flaviviridae family; however, now, HCV has been placed in a new monotypic genus, hepacivirus. Therefore, in one embodiment, the flavivirus or pestivirus is not HCV.
Nonlimiting examples of antiviral agents that can be used in combination with the compounds disclosed herein include:
(1) an interferon and/or ribavirin (Battaglia, A. M. et al., Ann. Pharmacother. 34:487-494, 2000); Berenguer, M. et al. Antivir. Ther. 3(Suppl. 3):125-136, 1998);
(2) Substrate-based NS3 protease inhibitors (Attwood et al., Antiviral peptide derivatives, PCT WO 98/22496, 1998; Attwood et al., Antiviral Chemistry and Chemotherapy 10.259-273, 1999; Attwood et al., Preparation and use of amino acid derivatives as anti-viral agents, German Patent Publication DE 19914474; Tung et al. Inhibitors of serine proteases, particularly hepatitis C virus NS3 protease, PCT WO 98/17679), including alphaketoamides and hydrazinoureas, and inhibitors that terminate in an electrophile such as a boronic acid or phosphonate. Llinas-Brunet et al, Hepatitis C inhibitor peptide analogues, PCT WO 99/07734.
(3) Non-substrate-based inhibitors such as 2,4,6-trihydroxy-3-nitro-benzamide derivatives (Sudo K. et al., Biochemical and Biophysical Research Communications, 238:643-647, 1997; Sudo K. et al. Antiviral Chemistry and Chemotherapy 9:186, 1998), including RD3-4082 and RD3-4078, the former substituted on the amide with a 14 carbon chain and the latter processing a para-phenoxyphenyl group;
(4) Thiazolidine derivatives which show relevant inhibition in a reverse-phase HPLC assay with an NS3/4A fusion protein and NS5A/5B substrate (Sudo K. et al., Antiviral Research 32:9-18, 1996), especially compound RD-1-6250, possessing a fused cinnamoyl moiety substituted with a long alkyl chain, RD4 6205 and RD4 6193;
(5) Thiazolidines and benzanilides identified in Kakiuchi N. et al. J. EBS Letters 421:217-220; Takeshita N. et al. Analytical Biochemistry 247:242-246, 1997;
(6) A phenan-threnequinone possessing activity against protease in a SDS-PAGE and autoradiography assay isolated from the fermentation culture broth of Streptomyces sp., Sch 68631 (Chu M. et al., Tetrahedron Letters 37:7229-7232, 1996), and Sch 351633, isolated from the fungus Penicillium griscofuluum, which demonstrates activity in a scintillation proximity assay (Chu M. et al., Bioorganic and Medicinal Chemistry Letters 9:1949-1952);
(7) Selective NS3 inhibitors based on the macromolecule elgin c, isolated from leech (Qasim M. A. et al., Biochemistry 36:1598-1607, 1997);
(8) Helicase inhibitors (Diana G. D. et al., Compounds, compositions and methods for treatment of hepatitis C, U.S. Pat. No. 5,633,358; Diana G. D. et al., Piperidine derivatives, pharmaceutical compositions thereof and their use in the treatment of hepatitis C, PCT WO 97/36554);
(9) Polymerase inhibitors such as nucleotide analogues, gliotoxin (Ferrari R. et al. Journal of Virology 73:1649-1654, 1999), and the natural product cerulenin (Lohmann V. et al., Virology 249:108-118, 1998);
(10) Antisense phosphorothioate oligodeoxynucleotides (S-ODN) complementary to sequence stretches in the 5xe2x80x2 non-coding region (NCR) of the virus (Alt M. et al., Hepatology 22:707-717, 1995), or nucleotides 326-348 comprising the 3xe2x80x2 end of the NCR and nucleotides 371-388 located in the core coding region of the IICV RNA (Alt M. et al., Archives of Virology 142:589-599, 1997; Galderisi U. et al., Journal of Cellular Physiology 181:251-257, 1999);
(11) Inhibitors of IRES-dependent translation (Ikeda N et al., Agent for the prevention and treatment of hepatitis C, Japanese Patent Publication JP-08268890; Kai Y. et al. Prevention and treatment of viral diseases, Japanese Patent Publication JP-10101591);
(12) Nuclease-resistant ribozymes. (Maccjak D. J. et al., Hepatology 30 abstract 995, 1999); and
(13) Other miscellaneous compounds including 1-amino-alkylcyclohexanes (U.S. Pat. No. 6,034,134 to Gold et al.), alkyl lipids (U.S. Pat. No. 5,922,757 to Chojkier et al), vitamin E and other antioxidants (U.S. Pat. No. 5,922,757 to Chojkier et al.), squalene, amantadine, bile acids (U.S. Pat. No. 5,846,964 to Ozeki et al.), N-(phosphonoacetyl)-L-aspartic acid, (U.S. Pat. No. 5,830,905 to Diana et al.), benzenedicarboxamides (U.S. Pat. No. 5,633,388 to Diana et al.), polyadenylic acid derivatives (U.S. Pat. No. 5,496,546 to Wang et al.), 2xe2x80x2,3xe2x80x2-dideoxyinosine (U.S. Pat. No. 5,026,687 to Yarchoan et al.), and benzimidazoles (U.S. Pat. No. 5,891,874 to Colacino et al.).